Experimental Analysis of Tensile Strength of Different Thicknesses and Dissimilar Aluminum Alloys in Friction Stir Welding

Recently, demands of the prefabricated tailor-welded blanks (TWBs) are being increased in the manufacturing of the structures of the aircraft panels. TWBs eliminate several operations of assembly process and reduce the consumption of material, time and cost. To manufacture the TWBs, friction stir welding process is gaining popularity because it reduces the common defects of the convention welding method. However, welding of similar and dissimilar material having different thicknesses is challenging by friction stir welding process. In this work, an attempt has been made to join the dissimilar material with different thickness ratios and also evaluate the performance of the weld joint with effect of input process parameters using surface response methodology. The experiments were conducted on the basis of Box–Behnken method design of experiments, in which three input factors are tool welding speed, rotation speed and tilt angle, and tensile strength of the joint is output response. Adequacy of the design of experiments is investigated by ANOVA analysis, and mathematical model is developed to determine the trend of the response surfaces of tensile strength to input factors. Additionally, microstructures of the weld joint are studied to analyze the material deposition process in the weld joint of the different thicknesses of the work piece material. This analysis shows that the tool tilt angle is one of the important factors among all input process parameters. The trend of the response surfaces of the tensile strength of the weld joint substantially varies on slight variation in the tool tilt angle. The highest tensile strength 302 MPa of the weld joint is obtained at 8 0 tool tilt angle, 900 rpm and 63 mm/min welding speed. The average grain size in stir zone of highest tensile strength weld joint is 6.01 μm, and lowest tensile strength weld joint is 13.99 μm.